Expandable intervertebral spacers

ABSTRACT

Laterally expanding vertebral spacer devices are provided for repairing damaged vertebral discs. The vertebral spacer devices maintain the height of a distracted vertebral disc space while providing stability to the spine. In one form of the invention, a vertebral spacer device is provided with a first arm movably coupled to a second arm. The first and second arms are laterally expandable from a first width for insertion into the disc space to a second width after insertion into the disc space. The first and second arms also define a cavity therebetween for placement of bone growth material.

REFERENCE TO RELATED APPLICATIONS

[0001] This application is a division of U.S. patent application Ser.No. 09/691,307, filed Oct. 18, 2000, now pending, which is a division ofU.S. patent application Ser. No. 09/182,560, filed Oct. 29, 1998, nowU.S. Pat. No. 6,193,757, issued Feb. 27, 2001, all of which areincorporated by reference in their entirety.

BACKGROUND OF THE INVENTION

[0002] The present invention is directed to implantable devices forstabilizing the spine. Specifically, the invention concernsintervertebral spacers expandable from a reduced size insertionconfiguration to an expanded size spacing configuration.

[0003] Intervertebral discs, located between the end plates of adjacentvertebrae, stabilize the spine, distribute forces between vertebrae andcushion vertebral bodies. An intervertebral disc may deteriorate due totrauma, aging or disease resulting in pain or discomfort to a patient.One common procedure for relief of patient discomfort is a discectomy,or surgical removal of a portion or all of an intervertebral disc.Often, this is followed by implantation of a device between adjacentvertebrae to maintain or restore disc space height. Typically,implantation of such a device is also intended to promote bony fusionbetween the adjacent vertebral bodies.

[0004] One limitation on the size of a device inserted into the discspace is the size of the opening through surrounding tissue that isavailable to gain access to the disc space. From a posterior approach tothe spine, the dura and nerve roots must be mobilized to gain access tothe disc space. Similarly, from an anterior approach, the aorta and venacava must be mobilized to gain access to the disc space. Suchmobilization is often limited by the anatomical structures, thusresulting in a relatively small access site. Removal of additional boneto enlarge an entrance to the disc space may weaken the joint betweentwo adjacent vertebra. Moreover, excessive retraction of vessels andneural structures to create a large access opening may damage thesetissues. Thus, prior procedures have been limited to placing a firstdevice passable through the available opening on one side of the spineand mobilizing the tissue or vessels to place another similar implant onthe opposite side of the spine. Each implant being limited in size bythe available access site.

[0005] Thus, there remains a need for implantable devices that have areduced size insertion form and are expandable in the disc space to alarger size for enhancing spine stability and facilitatingimmobilization via bony fusion.

SUMMARY OF THE INVENTION

[0006] The present invention contemplates an intervertebral spacerdevice that has a reduced size configuration for insertion into a discspace and an expanded size configuration to maintain the spacing of thedisc space. In one aspect of the present invention, the device includesa pair of arms each having a first end and a second end, the arms beingmovably coupled at their first ends. When the arms are positionedadjacent one another, the device is in a reduced size configuration forinsertion into the disc annulus. The device is laterally expandable inthe disc space to an expanded configuration by moving the pair of armsabout the first ends in order to increase the dimension of the deviceperpendicular to the longitudinal axis of the spine while maintainingthe inter-space distraction. Preferably, the expanded device creates acavity that may be filled with bone or bone substitute material forpurposes of promoting fusion between the adjacent vertebrae. Preferably,the height of the device in the reduced size configuration issubstantially the same as the height in the expanded configuration, withthe expanded configuration providing an increased base of support.

[0007] In another embodiment of the present invention, the first andsecond arms each have laterally extending portions extending therefromthat cooperate to engage the first and second arms to one another.Preferably, each of the laterally extending portions defines a pluralityof serrations, wherein the serrations of one laterally extending portionof the first arm cooperate in interdigiting fashion with serrations ofthe corresponding laterally extending portion of the second arm. In onepreferred embodiment, the laterally extending portions are provided atthe first and second ends of each of the arms. In another preferredembodiment, the pair of arms are pivotably coupled at their first ends,and laterally extending portions are provided at the second ends.

[0008] In still a further embodiment, the pair of arms are flexiblyattached such that they are compressible into a first smallerconfiguration and laterally self-expand to a second largerconfiguration. In one such embodiment, the arms are interconnected by aflexible hinge portion at one end of each arm. In another embodiment,each arm is flexibly connected to a first end portion and an opposingsecond end portion to form a substantially rectangular shape havingflexible side walls. Preferably, the side walls are biased to assume thesecond larger configuration.

[0009] One object of the present invention is to provide a vertebralspacer device that is capable of insertion in a smaller form andlaterally expandable within the disc space to an enlarged configurationfor supporting the spine.

[0010] Other objects and advantages of the present invention will bereadily discerned upon consideration of the following writtendescription and accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011]FIG. 1. is a perspective view of one embodiment of a vertebralspacer device according to the present invention.

[0012]FIG. 2 is a top view of the vertebral spacer device of FIG. 1.

[0013]FIG. 3 is a left end view of the vertebral spacer device of FIG.2.

[0014]FIG. 4 is a right end view of the vertebral spacer device of FIG.2.

[0015]FIG. 5 is an elevational view of the vertebral spacer device ofFIG. 2.

[0016]FIG. 6 is a top view of the vertebral spacer of FIG. 1 shown in anexpanded position.

[0017]FIG. 7 is an anterior-posterior view of a pair of vertebrae havinga collapsed disc space therebetween.

[0018]FIG. 8 is an anterior-posterior view of the vertebrae of FIG. 7showing the vertebrae after distraction of the disc space.

[0019]FIG. 9a is a partial cross-sectional top view of the vertebrae ofFIG. 8 with the vertebral spacer device of FIG. 1 in an expandedposition between the vertebrae.

[0020]FIG. 9b is a partial cross-sectional top view of a vertebral bodyas shown in FIG. 8, with a pair of vertebral spacer devices according toFIG. 1 inserted from a bilateral posterior approach.

[0021]FIG. 9c shows the vertebral spacer devices of FIG. 9b in anexpanded configuration.

[0022]FIG. 10 is a side view of an insertion tool useable with thevertebral spacer devices of the present invention.

[0023]FIG. 10a is an end view of the insertion tool of FIG. 10.

[0024]FIG. 11 is a perspective view of an expansion tool useable withthe vertebral spacer devices of the present invention.

[0025]FIG. 12 is a perspective view of an element of FIG. 11.

[0026]FIG. 13 is a perspective view of an alternate embodiment vertebralspacer device according to the present invention.

[0027]FIG. 14 is a top plan view of the vertebral spacer device of FIG.13 in an unexpanded position.

[0028]FIG. 15 is a top plan view of the vertebral spacer device of FIG.13 in an expanded position.

[0029]FIG. 16 is a cross-sectional view of the vertebral spacer deviceof FIG. 14 taken along line 16-16.

[0030]FIG. 17 is a partial cross-sectional side view of an insertiontool device usable with the vertebral spacer device of FIG. 13.

[0031]FIG. 18a is a perspective view of another embodiment of avertebral spacer device according to the present invention.

[0032]FIG. 18b is a perspective view of the vertebral spacer device ofFIG. 18a constrained within a delivery system.

[0033]FIG. 19a is a top view of a laterally expandable implant accordingto another embodiment of the present invention.

[0034]FIG. 19b is a top view of the implant of FIG. 19a in a compressedconfiguration.

[0035]FIG. 19c is a side view of the implant of FIG. 19a.

[0036]FIG. 20a is a perspective view of another embodiment of avertebral spacer device according to the present invention.

[0037]FIG. 20b is a perspective view of the space device of FIG. 20awithout the ratchet mechanism.

[0038]FIG. 21 is a perspective view of yet another embodiment of avertebral spacer device according to the present invention.

[0039]FIG. 22 is a perspective view of yet another embodiment of avertebral spacer device according to the present invention.

[0040]FIG. 23 is a plan view of an expansion tool usable with thevertebral spacers of FIGS. 20-23.

[0041]FIG. 23a is a fragmentary perspective view of a portion of theinsertion tool device of FIG. 23.

[0042]FIG. 24 is a perspective view of another embodiment of a vertebralspacer device according to the present invention shown in a collapsedposition.

[0043]FIG. 24a is a perspective view of the vertebral spacer device ofFIG. 22 shown in an expanded position.

[0044]FIG. 25 is a perspective view of yet another embodiment of avertebral spacer device according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0045] For the purposes of promoting an understanding of the principlesof the invention, reference will now be made to the embodimentsillustrated in the drawings and specific language will be used todescribe the same. It will nevertheless be understood that no limitationof the scope of the invention is thereby intended, any alterations andfurther modifications in the illustrated devices, and any furtherapplications of the principles of the invention as illustrated thereinbeing contemplated as would normally occur to one skilled in the art towhich the invention relates.

[0046] In accordance with one embodiment of the invention, a vertebralspacer device 50 is depicted in FIGS. 1-6. Device 50 includes a firstlateral arm 52 and a second lateral arm 54. First arm 52 includes afirst end 60 and an opposite connection end 61. Second arm 54 includes afirst end 62 and an opposite connection end 63. First arm connection end61 is fixedly coupled to second arm connection end 63 via connection pin58 extending through a bore 59 defined through connection ends 61 and63. Bore 59 extends transverse to the longitudinal axis 53 of spacer 50.

[0047] First arm 52 and second arm 54 each define a portion of a topbone engaging surface 56 adapted to engage a vertebral body and aportion of bottom bone engaging surface 57 substantially identical totop bone engaging surface 56. When first arm 52 and second arm 54 are inan opened position, as shown in FIG. 6, a central cavity 66 is definedtherebetween. Cavity 66 is adapted to receive a graft or bone-growthinducing material therein.

[0048] Referring now to FIGS. 3-6, the vertebral spacer device 50 isillustrated and described below in further detail. Connection end 63 ofsecond arm 54 is fixedly coupled to connection end 61 of first arm 52via connection pin 58 extending through bore 59. However, it should beunderstood that any type of connection mechanism contemplated herein,provide the principles of the current invention are adhered to. As anexample, but without limitation, an alternative connection mechanism maybe a hinge between and fixedly engaging first arm 52 and second arm 54to allow pivotal movement therebetween. Alternatively, first and secondarms may be integrally formed of a flexible material, thereby permittingmovement at the connection point.

[0049] First end 60 of first arm 52 and first end 62 of second arm 54each define a corresponding socket portion 64 and 65, respectively. Whendevice 50 is in a first closed position, as shown in FIG. 4, socketportions 64 and 65 define a socket for 67 for receiving a driving tool,which will be described more fully below. End 60 also includes aninternally threaded bore 68 defined by device 50. Threaded bore 68 isprovided to receive an attachment portion of an insertion toolconfigured for manipulation of device 50 into and out of a disc space.

[0050] It should be noted that in the illustrated embodiment first arm52 and second arm 54 are configured such that the top bone engagingsurface 56 defined on each of the arms 52 and 54 extends in asubstantially uniform horizontal plane to make the bone engaging surface56 substantially planar in a first plane. The bottom bone engagingsurface 57 defined by arms 52 and 54 also extends in a substantiallyuniform horizontal plane making the bottom bone engaging surface 57substantially planer in a second plane. In a preferred embodiment, thefirst and second planes are generally parallel and separated by aheight. Preferably, the height between the first and second planes issubstantially constant between the closed position of FIG. 2 and theopen positions of FIGS. 6 and 9. Thus, the disc space height duringinsertion may be substantially maintained in the expanded position.

[0051] Device 50 may be positioned in a closed position forming areduced size configuration shown in FIGS. 2-4. Preferably, arms 52 and54 are closely adjacent in this position, although the exact armpositioning may vary depending on the application. In the closedposition, device 50 has a lateral width W₁ extending transverse tolongitudinal axis 53 of the device.

[0052] Device 50 may be positioned in an open position forming anexpanded size configuration as shown in FIGS. 1, 6 and 9. The extent ofdistance between first arm 52 and second arm 54 may be varied dependingon the expanded size desired. In the open position, device 50 may haveat least a lateral width W₂ extending transverse to longitudinal axis 53of the device. Lateral width W₂ being greater than lateral width W₁. Asshown in FIG. 9a, the lateral width in the expanded configuration may besubstantially greater than width W₁. This expanded width provides a muchwider base of support than the device does in the closed position. Thewider base of support provides greater stability of the device.

[0053] Referring to FIG. 9b, there is shown a vertebral body with twolaterally expandable implants according to the present invention.Implants 70 and 72, slightly smaller versions of device 50, have beeninserted through posterior openings 74 and 76, respectively, into thedisc space in their reduced size insertion form. It will be understoodthat this placement is approximately in the same position in the discspace into which known devices may be placed. In much the same mannerthat chairs, such as tall stools, are subject to tipping if the legs aretoo close, implants may also be subject to tipping if they lack asufficiently wide base support area. However, referring to FIG. 9c, thepresent invention permits each of devices 70 and 72 to be expanded inthe disc space to a greater width, thereby increasing the total width ofthe base of support. Moreover, material G promoting bone growth may beplaced in the cavity between the arms and around the exterior of theimplants.

[0054] The bone engaging surfaces 56 and 57 of device 50 are configuredto provide an even distribution and transfer of the load from the uppervertebral body through the integral side walls of device 50 to the lowervertebral body. In a preferred embodiment, the endface plates 56 and 57are knurled to provide frictional engagement between the vertebrae andthe device 50. While knurling is shown as one configuration for the boneengaging surface, other configurations may be utilized. For example, butwithout limitation, grooves may be formed on the upper and lower boneengaging surfaces extending transverse to longitudinal axis 53 to resistexpulsion. More specifically, arcuate grooves may be formed having aradius of curvature originating at pin 58 to follow the arc of the armsas they are expanded in the disc space to form the expanded openposition shown in FIG. 6.

[0055] Referring to FIGS. 7-9, a spinal segment with vertebrae V₁ and V₂is illustrated to briefly describe a surgical procedure in which device50 may be employed. More specifically, in FIG. 7 a damaged or diseasedspinal segment is shown without the device 50. D1 represents adegenerated or damaged disc between vertebrae V₁ and vertebrae V₂ thathas resulted in the collapse of the disc space between the vertebrae.Vertebrae V₁ and V₂ form part of a spinal column having a longitudinalaxis L extending therethrough.

[0056] In FIG. 8, the vertebrae V₁ and V₂ are shown distracted such thatthe disc space is restored to approximately its normal height,represented by distracted disc space D2. Tensioning of annularstructures that extend between DI and D2 promotes disc stability. Alsoshown is an opening A made in the annulus fibrosus that may be createdby the surgeon by an annulotomy or disectomy surgical procedure to gainaccess to the disc space from an anterior approach. As known in the artand not further described herein, the adjacent end plates of V₁ and V₂may be prepared to promote bone fusion therebetween and accept device50. Device 50 is inserted through opening A while in the reduced sizeconfiguration (as shown in FIGS. 2 through 4). Once inserted into thedisc space, the device 50 is laterally expanded to expanded sizeconfiguration (as shown in FIGS. 1 and 6) by moving first arm 52 inrelation to second arm 54 in the disc space. The lateral expansion ofdevice 50 increases the lateral dimension of device 50 in a directiontransverse to longitudinal axis L, while maintaining the height ofdistracted disc space D2. In FIG. 9 the device 50 is shown in plan viewinserted into D2 between vertebrae V₁ and V₂ through opening A. It willbe understood that use of the laterally expandable implant according tothe present invention limits the amount of mobilization of overlappingvessels and permits insertion of an implant having a much wider spacingconfiguration than would otherwise be implantable with a non-expandingimplant.

[0057] The expanded configuration of device 50 creates cavity 66 thatmay then be filled with a bone graft material or bone-growth inducingmaterial G for the purposes of promoting fusion between vertebrae V₁ andV₂. The graft material G also helps to maintain the device 50 in thelaterally expanded configuration. As can be seen in FIG. 9, the expandeddevice 50 is larger than the opening A made through the annulusfibrosus. Thus, in addition to the knurled endface plates 56 and 57, theremaining annulus fibrosis may also act to limit displacement of device50 from the disc space. While the device has been inserted with thewider end adjacent opening A, it is contemplated that the connection endmay be disposed adjacent the opening. For this use, a biasing element,such as a spring, may be disposed between the arms to urge them to theexpanded condition.

[0058] FIGS. 7-9 c illustrate two methods for inserting laterallyexpandable devices into the disc space D2. The present invention alsocontemplates the use of additional methods as known in the art forinserting interbody fusion implants. For example, more than onevertebral spacer device may be inserted through the same opening A. Forexample, a first device 50 could be inserted and laterally expanded, andpacked with bone graft material. Then a second device may be inserted inthe disc space and between the arms of the first device. The seconddevice may be laterally expanded and packed with bone graft material G.

[0059] Referring to FIGS. 9aand 9 b, there is shown a vertebral bodywith two implants positioned in the disc space. In this procedure,bilateral access to the disc space is achieved by posterior openings 74and 76. It will be understood that the size of openings may be limitedby the amount of dural compression that may be safely achieved, nerveroot location and the amount of bone removed adjacent the disc space.Devices 70 and 72 are inserted via opening 74 and 76, respectively. Thedevices are inserted into the disc space in the reduced sizeconfiguration. Once disposed in the disc space, devices 70 and 72 areexpanded and graft material is positioned in the cavity formed betweenthe arms. Preferably, as shown in FIG. 9c, material may be positionedbetween the implants before one or both are expanded to provide afurther area for bone growth. While a device according to FIG. 1 hasbeen shown for the purposes of illustrating the methods of insertion, itis contemplated that the other embodiments disclosed herein may beinserted in a like manner.

[0060] Referring now to FIGS. 10-12, various instruments useful forinsertion and lateral expansion of device 50 are shown therein. Theinsertion tool 260 of FIG. 10 is useable for insertion of device 50 intothe disc space. Insertion tool 260 includes a handle portion 262, athreaded stem portion 266, and rod 264 extending between handle 262 andthreaded portion 266. A sleeve 268 is slidably disposed about the stem264. Sleeve 268 includes protrusion 270 extending therefrom and adaptedto engage cavity 67 in device 50. While not illustrated, device 260 mayinclude a stop mechanism operable to prevent sliding of sleeve 268 aboutrod 264 after device 50 is engaged thereto.

[0061] To use insertion tool 260 to insert the implant device 50,threaded portion 266 threadedly engages device 50 via threaded bore 68.Once the device 50 is threadedly engaged to insertion tool 260, sleeve268 may be slid down rod 264 toward the device 50 until protrusion 270resides within cavity 67. Rod 264 and protrusion 270 prevent rotationbetween device 50 and insertion tool 260 during insertion. The vertebralspacer device 50 may then be inserted into a prepared disc space usingthe insertion tool 260. Once device 50 is placed in the disc space,sleeve 268 may be retracted towards handle 262 to disengage protrusion270 from cavity 67. Threaded stem portion 266 may then be removed fromthreaded bore 68. Alternatively, if it is desired to remove the device50 from the disc space after initial insertion or to reposition thedevice 50 within the disc space, the threaded stem portion 266 allowsthe device 50 to be withdrawn or repositioned. It is contemplated hereinthat insertion of device 50 into the disc space via insertion tool 260is accomplished with device 50 in a closed position, as shown in FIG. 2.

[0062] Once the device 50 is inserted into the desired position in thedisc space, first arm 52 and second arm 54 may be laterally expanded toincrease the lateral dimension of device 50 with respect to spinallongitudinal axis L in order to stabilize the spinal column and fill alarger portion of the disc space. In a preferred embodiment, each boneengaging surface 56 and 57 includes a beveled edge around the perimeterof device 50. The beveled edge facilitates insertion between adjacentvertebrae and eases expansion in the disc space.

[0063]FIG. 11 illustrates one type of driving tool 250 operable to atleast initially laterally expand device 50 to a laterally expandedconfiguration. Driving tool 250 includes T-handle portion 254, a squaredriving end 258 adapted to engage cavity 67, and a hollow tube 256extending between handle portion 254 and driving end 258. In order tolaterally expand device 50, driving tool 250 is rotated via the T-handle254 with driving end 258 disposed within cavity 67. Rotation of drivingend 258 causes first arm 52 and second arm 54 to move laterally withrespect to one another in a manner that laterally expands the arms 52and 54 of device 50.

[0064] In order to further laterally expand first arm 52 and second arm54, a spreader 280 as shown in FIG. 12 may be used in conjunction withtool 250. Spreader 280 includes a first end 282, a wedge portion 286,and stem 284 extending therebetween. As shown in FIG. 11, spreader 280may be disposed within hollow tube 256 and advanced beyond its distalend to more fully expand the device. Wedge portion 286 may be placedbetween first arm 52 and second arm 54. A force applied to first end 282drives wedge portion 286 between arms 52, 54 in order to furtherlaterally expand the device 50.

[0065] While the above-described spreader is disclosed as a preferredembodiment, it is contemplated that other instruments may be used toexpand the device without deviating from the scope of the invention.Specifically, spreader 280 may be used may be used alone to laterallyspread the expandable device.

[0066] As shown in FIGS. 6 and 9, when device 50 is in a laterallyexpanded position, a cavity 66 is formed between first arm 52 and secondarm 54. A graft material G may then be placed or packed into cavity 66.The graft material G could be cancellous bone or bone chips, or asuitable bone graft substitute material known to those skilled in theart. One advantage of the device 50 is that it allows bone graftmaterial G to be placed at or near the central portion of the vertebraewhile the expandable spacer engages more lateral portions of thevertebra. This central portion is known to be highly vascular andbiologically active, so that it is an excellent location for bone graftincorporation and fusion. In addition, bone-growth enhancing materialsmay be introduced with the graft material to enhance initial andultimate fusion of the vertebrae V₁ and V₂.

[0067] It should be appreciated that device 50 may be delivered to thedisc space for insertion through a cannula employed in aminimally-invasive surgical technique. Device 50 is sized for placementthrough the cannula in its unexpanded configuration. Once positioned inthe disc space, the lateral dimension of the device is increased byexpanding the first and second arms 52, 54 as described above. Othersurgical techniques for insertion are contemplated, for example, opensurgical procedures with direct access to the spine. Device 50 thusallows minimization of the size of the entry into the disc space and theresulting damage to tissue surrounding the surgical site. Further, thereduced size configuration of the implant permits insertion of arelatively large spacer where anatomical features, such as the dura,nerve roots or blood vessels, would have prevented placement of alarger, non-expanding sized spacer.

[0068] Referring now to FIGS. 13-16, another embodiment of the presentinvention is illustrated. The expandable vertebral spacer 80 includes afirst arm 82 having a distal end 90, and a second arm 84. Second arm 84is movable coupled to main body portion 82 via hinge portion 98. Firstarm 82 is provided with a tapering guide 88 protruding therefrom as itextends from hinge portion 98 towards distal end 90. Guide 88 isreceived within a recess 86 defined in second arm 84. Vertebral spacer80 also defines tool receiving opening 99 defined in hinge 98. Toolreceiving opening 99 is configured to have an internal thread toaccommodate an insertion tool, such as tool 300 illustrated in FIG. 17.

[0069] Second arm 84 includes a locking arm 94 adjacent its distal endthat is integrally formed with laterally expandable portion 84 vialocking arm hinge portion 95. Locking arm 94 is configured to bepositioned adjacent distal end portion 90 in the closed position shownin FIG. 14. In the closed position the device is in a reduced sizeconfiguration suitable for insertion. In this configuration, device 80has a lateral width W₃ extending transverse to the longitudinally axisof the device. Preferably, spacer 80 is formed of an at least partiallyresilient material and distal end portion 90 may be biased toward cavity85. In this configuration the arms tend to move to the locked positiononce the spacer is sufficiently expanded. Distal end portion 90 includesa catch 92 formed thereon, and locking arm 94 includes a catch-receivingportion 96. When the device 80 is laterally expanded to a second lateralposition, as shown in FIG. 15, locking arm hinge 95 urges locking arm 94towards distal end portion 90 until catch-receiving portion 94 engagescatch 92. Catch 92 prevents displacement of expandable portion 84towards main body portion 82 after the device 80 is inserted in the discspace. The device 80 is then held in the expanded position, and cavity85 may be packed with bone growth material through opening 99. Furtheropenings for bone ingrowth or bone growth material packing may beprovided. In the laterally expanded configuration of FIG. 15, device 80has a maximum lateral width W₄, width W₄ being greater than W₃.

[0070] It should be noted that the device 80 defines a top vertebralbearing surface 97 and a bottom vertebral bearing surface 93. Thebearing surfaces 93 and 97 are composed of the surfaces provided onfirst arm 82, second arm 84, and hinge 98. In a preferred embodiment,bearing surfaces 93 and 97 are spaced apart a height that remainsrelatively constant from the closed to expanded positions. The bearingsurfaces contact the adjacent vertebrae endplates to provide an evendistribution of loads through the endplates and balanced loadingconditions. While not shown, it will be understood that these surfacesmay include roughening to inhibit expulsion.

[0071] It is contemplated that devices according to the presentinvention may be manufactured from bio-compatible materials having atleast some flexibility without fracture. Further, it is anticipated thatportions of bone may be used provided the hinge points have been atleast partially demineralized to provide flexibility. Demineralizationof bone is known in the art and will not be described further herein.More preferably, device 80 is formed from material having a degree ofresiliency tending to urge locking arm 94 into the locking position withthe catch 92 engaged with catch-receiving portion 94. Such materials mayinclude, but are not limited to, stainless steel, shape memory alloys,composites and plastics. Moreover, while flexible hinge portions havebeen disclosed, it will be understood that hinge pin and channelconnections may replace the flexible hinges without deviation from thespirit of the invention. Optionally, a biasing mechanism, such as aspring, may be placed between the arms to urge the device to theexpanded configuration.

[0072] The present invention also contemplates an instrument forinserting and expanding an implant according to the present invention.Referring now to FIG. 17, an insertion tool 300 is illustrated. Tool 300includes a hollow outer sleeve 302 that receives a portion of an innersleeve 304. Inner sleeve 304 defines connecting portion 322 that engagesmating portion 320 of outer sleeve 302. In the illustrated embodiment,inner sleeve 304 is threadedly received within the outer sleeve 302.Inner sleeve 304 further defines an opening 324 therethrough forreceiving rod 310. Inner sleeve 304 also includes a pair of movable arms306 and 308 having gripping portions 309 and 311, respectively,configured for holding device 80 during insertion. In order for arms 306and 308 to grip the device 80, outer 302 is moved with respect to innerhandle 304 such that inclined portion 318 of outer sleeve 302 urgesgripping portions 309 and 311 of arms 306 and 308 against device 80. Inthe illustrated device 300, this accomplished by rotating outer handle302 about a thread on connecting portion 322 towards the device 80.

[0073] Once device is engaged by gripping portions 309 and 311, it maybe inserted into the disc space. After insertion of device 80 to thedesired location, rod 310 is operable to laterally expand device 80. Rod310 has a handle portion 312, and opposite a threaded portion 314, and ashaft 313 extending therebetween. In a preferred embodiment, shaft 313has a distal end 316 that is beveled to engage the inclined surfaces 87and 89 of first arm 82 and second arm 84, respectively. Handle 310 maybe engaged with device 80 during insertion into the disc space viathreaded engage with tool receiving opening 99. The threaded engagementbetween threaded portion 314 and the device 80 allows the device 80 tobe positioned within the disc space. In order to position the device 80to its expanded configuration, mechanism 310 is threaded withinreceiving portion 99 in order to urge distal end 316 against surfaces 87and 89 to laterally expand device 80 to the expanded or second lateralconfiguration as shown in FIG. 15.

[0074] While the above-described spacer embodiments of FIGS. 1 and 13have been described as having a first arm and a second arm movablecoupled, it will be understood that the invention contemplates a mainbody portion and laterally expandable portion movably coupled thereto.Specifically, while first arm and second arm may simultaneously movelaterally to form the expanded configuration, it is contemplated thatone arm may remain stationary while the other arm moves. Moreover, thedevice may be formed such that the device includes a stationary mainbody with one or more movable laterally expandable portions movable togive the device both a reduced size configuration and a laterallyexpanded size configuration.

[0075] Referring now to FIGS. 18a and 18 b, another embodiment of thepresent invention is illustrated. Vertebral spacer device 100 includes apair of lateral arms 102 and 103 extending between a distal end 106 anda proximal end 108. The device 100 includes a top vertebral bearingsurface 112 and an identical bottom vertebral bearing surface (notshown). A central cavity 114 is formed between the lateral arms 102. Thedevice 100 also includes openings 104 and 105 defined by lateral arms102 and 103, respectively. Openings 104 and 105 permit communicationbetween the interior and exterior of the device and reduce the materialin walls 102 and 103, thereby increasing the flexibility of device 100.Device 100 also includes at least one insertion tool opening 110 formedin proximal end 108. Preferably, opening 110 is threaded to receive acorrespondingly threaded insertion tool (not shown).

[0076] The embodiment of FIG. 18 is preferably formed of a resilientlyflexible material. Such materials may include, without limitation,bio-compatible metals (including shape memory alloys), composites, andplastics. In a preferred embodiment, the device 100 is expanded andcontracted by making the device 100 from a shape memory material, suchas nitinol, exhibiting super elasticity and/or temperature induced shapememory. The device 100 is initially formed in a laterally expanded orsecond position. In order to insert the device 100 through a smallopening and into the disc space, it is contracted to a first lateralposition by applying a force to lateral arms 102 and 103 in thedirection indicated by the arrows “R”. Thus, the device is laterallycompressed into a smaller sized configuration. Often, the device willexperience some elongation, as shown by dimension “I”. When the deviceis contracted, as shown in FIG. 19, it may be inserted through a tubulardelivery system, such as the cannula 120. Once the device is inserted inthe disc space, it is no longer confined by the cannula 120, and itself-expands laterally to a second position within the disc spaceapproximating its pre-insertion condition. Cavity 114 may be filled withbone growth material delivered through opening 110. Cavity 114 may alsobe partially loaded with bone growth material prior to insertion. It isalso contemplated herein that device 100 may be inserted into the discspace without use of cannula 120, such as by an open surgical procedure.Temporary compression may be achieved by an external device such as, butwithout limitation, pliers adapted to compress the implant.

[0077]FIGS. 19athrough 19 c illustrate a further embodiment of alaterally expandable spacer according to the present invention. Spacer121 includes arms 122 and 123 connected by a flexible portion. Arm 122terminates in an end wall 125 and arm 123 terminates in an end wall 126.As shown in FIG. 19b, the respective lengths of arms 122 and 123 allowend wall 126 to nest within end wall 125.

[0078] Spacer 121 is preferably formed of a flexible and resilientmaterial. The spacer is in a relaxed form in the expanded configurationof FIG. 19a having a lateral width W₆. Width W₆ is decreased to lateralwidth W₅ by the application of compressive force on arms 122 and 123urging end walls 125 and 126 towards one another. Preferably, spacer 121self-expands from the reduced size configuration of FIG. 19b to theexpanded configuration of 19 a. Preferably W₆ is approximately twice W₅,although a greater or lesser amount of lateral expansion may beprovided. Preferably, spacer 121 is formed of a fiber reinforced polymercomposite. The fibers, shown by the parallel shading marks in FIGS. 19athrough 19 c, extend generally parallel to the length of side walls 122and 123. It will be understood that this arrangement of fibers providesa degree of flexibility between the arms but resists compression fromthe upper to lower surfaces engaging the vertebral bodies.

[0079] Referring to FIG. 20a, another embodiment of a vertebral spacerdevice is illustrated. Vertebral spacer device 130 includes a first arm132 and a second arm 134 fixedly connected via hinge portion 136. Inthis embodiment, hinge portion 136 is integrally formed with first arm132 and second arm 134. First arm 132 includes first lateral extendingportion 138, and second arm 134 includes a second laterally extendingportion 140. First laterally extending portion 138 includes firstserrations 139 and second laterally extending portion 140 includescorresponding second serrations 141 disposed adjacent first serrations139. Serrations 139 and 141 cooperate in interdigiting fashion torestrain lateral contracting of the first arm 132 with respect to thesecond arm 134. The device 130 also includes tool opening 142, whichallows engagement of device 130 to insertion and/or expansion tools. Aspreviously disclosed, opening 142 may be threaded to receive acorresponding threaded tool. As with earlier disclosed embodiments,device 130 also defines a cavity 146, and includes substantially planarvertebral bearing surfaces 148 and 149 for engaging respective endplates of adjacent vertebrae.

[0080] The device 130 is shown in a contracted position, and onceinserted the device may be expanded by applying a force in the directionof the arrows “R”. The interdigiting serrations 139 and 141 must yieldsufficiently to allow movement of first arm 132 with respect to secondarm 134, while maintaining the separation of arm 132 and second arm 134when the force is removed.

[0081]FIG. 20b represents a modified version of FIG. 20a lackingserrations 139 and 141. Preferably, spacer 130 is formed of a flexiblematerial that may be plastically deformed. Thus, force applied to arms132 and 134 to expand the device plastically deforms hinge portion 136.Plastic deformation of hinge portion 136 maintains the device in theexpanded condition.

[0082]FIG. 21 illustrates another embodiment of the vertebral spacerdevice of the present invention. Device 150 includes a first arm 152 anda second arm 154. The term arm as used throughout the disclosure is usedbroadly to define sections and portions of devices. Arms may notnecessarily move within a device configuration. First arm 152 includes afirst extension 158 and a second extension 155. Second arm 154 includesthird extension 156 and fourth extension 166. First arm 152 is sized toreceive extensions 156 and 166 within extensions 158 and 155. Firstextension 158 defines first serrations 159 and second extension definessecond serrations 161. Third extension 156 defines third serrations 157and fourth extension 166 defines fourth serrations 168. First serrations159 and third serrations 157 cooperate in interdigiting fashion incooperation with interdigiting engagement of second serrations 161 andfourth serrations 168 to maintain lateral spacing between first arm 152and second arm 154. Device 150 also defines an upper vertebral engagingsurface 164, and an identical lower vertebral engaging surface, and toolopenings 160. Device 150 also defines a cavity 162, which may be filledwith bone growth material. Once the device 150 is inserted into the discspace, it may be expanded by applying force in the direction indicatedby arrow “R” to move first arm 152 with respect to second arm 154.

[0083] Referring now to FIG. 22, yet another embodiment of a vertebralspacer device in accordance with the present invention is illustrated.Device 170 includes a first arm 172 and a second arm 174. First arm 172includes first a pair of extensions 176 and second arm 174 includes apair of extensions 178. Extensions 176 include projections 175, andextensions 178 define receptacles 177. Projections 175 are configured tobe placed within a respective one of receptacles 177. Projections 178define first serrations 179 thereon, and receptacle 177 define secondserrations 181 thereon. First serrations 179 and second serrations 181cooperate in interdigiting fashion to resist displacement at first arm172 with respect to second arm 174. However, first serrations 179 andsecond serrations 181 yield sufficiently to allow lateral expansion ofthe device 170. Device 170 includes an upper vertebral engaging surface186 and an identical lower vertebral engaging surface. Arms 172 and 174define a central cavity 182 for receiving bone growth material.

[0084] A tool 340 for expanding the devices illustrated in FIGS. 20-22is illustrated in FIGS. 23 and 23a. Tool 340 includes a first lever 350pivotably coupled to a second lever 360 by pin 346. First lever 350includes a first handle portion 351 pivotably coupled to a firstextension 353 via pin 352. Second lever 360 has a second handle portion361 pivotably coupled to a second extension 363 via pin 362. Extensions353 and 363 are pivotable engaged via pin 348. Handle 340 also includesratchet mechanism 342 coupled to one of the handle portions 351, 361. Inthe illustrated embodiment, ratchet mechanism 342 is coupled to secondhandle portion 361 via pin 344. Ratchet mechanism 342 has teeth 346 forengaging first handle portion 351. Ratchet mechanism 342 is operable tomaintain the relative spacing between handle portions 351 and 361 whenengaged thereto.

[0085] First extension 353 has a first engagement portion 354 and secondextension 363 has a cooperable second engagement portion 364 located atrespective distal ends of each extension 353 and 363. First engagementportion 354 includes a first coupling 356, and second engagement portion364 includes a second coupling 366, each for coupling respective leverarms 350 and 360 to a vertebral spacer device, such as device 150illustrated in FIG. 21. Couplings 356 and 366 extend through acorresponding one of tool openings 160 to engage the device 150. Asshown in detail in FIG. 23a with respect to first engagement portion354, first and second couplings 356 and 366 each include a first andsecond head 358 and 368 and a first and second recess 359 and 369,positioned between first and second extensions 353 and 363,respectively. The first and second recesses 359 and 369 are configuredto receive a portion of the arms 152 and 154 therein to allow head 358and 368 to engage the device 150. The device 150 may then be laterallyexpanded or contracted as needed by manipulation of first and secondlever arms 351 and 361. Tool 340 may then be uncoupled from device 150by withdrawing the first and second coupling 356 and 366 from device150.

[0086] Referring now to FIGS. 24-24 a, another embodiment of a vertebralspacer device according to the present invention is illustrated. Device190 includes first arm 192 and second arm 194. First arm 192 ispivotally coupled to second arm 194 via sidewalls 196 extendingtherebetween. In the illustrated embodiment, two sidewalls 196 are shownwith one at the proximal end of the device 190 and the other sidewall196 at the distal end of device 190. The first and second arms 192 and194 are engaged to sidewalls 196 via hinge pins 197. The device 190 alsodefines an upper vertebral engaging surface 200 and a lower vertebralengaging surface, and tool insertion openings 198. In one embodiment,the device 190 is provided with ridges 204 extending from vertebralengaging surfaces for engaging the adjacent vertebral endface plates. Acentral cavity 202 for receipt of bone growth material is defined by thesidewalls 96, first arm 192, and second arm 194.

[0087] As shown in FIG. 24, the device 190 is collapsible to a firstreduced size configuration for insertion into the disc space having alateral width W₇. Once the device is inserted, it may be pivoted abouthinge portions 197 to an expanded position having greater width W₈ asshown in FIG. 24a. The device may be expanded by a tool inserted throughone or more of the openings 198. Bone growth material may be placed incavity 202 through openings 198.

[0088] Another embodiment of the vertebral spacer device of the presentinvention is illustrated in FIG. 25. The vertebral spacer device 210includes a first arm 212 and a second arm 214. First arm 212 includes afirst laterally extending portion 215, and second arm 214 includes asecond laterally extending portion 216. Second arm 214 also includesoffset portion 217 extending to engage first arm 212 at connection 226.Preferably, connection 226 is a hinge-type connection. The device 210also includes vertebral engagement surfaces 220 and 221 and, in apreferred embodiment, ridges 224 for engaging vertebral endface platesafter insertion. A central cavity 222 is formed between first arm 212and second arm 214. Bone growth material may be placed in central cavity222. Openings 218 may also be provided in the device for receivingvarious tools for inserting and expanding the device. A force applied inthe direction indicated by the arrows “R” will act to expand the device210 from the first reduced size lateral position of FIG. 25 to a secondexpanded lateral position (not shown) after insertion of the device 210into the disc space.

[0089] The vertebral spacers of the present invention may be placed andmaintained in position within the disc space by additional fixation. Thevertebral spacer devices are generally retained in position by thecompressive forces of the vertebral bodies acting on the bone engagingsurfaces of the implant. The spacer devices are preferably configured totransmit the compressive forces from the upper vertebral body directlythrough a one-piece side wall to the lower vertebral body and to limitconcentration of compressive loads at the movable couplings of the arms.Moreover, it is contemplated herein that fixation devices may be used inconjunction with the vertebral spacer device of the present invention.Alternatively, the vertebral spacer devices may be provided with anopening for receiving a fixation device, such as a bone screw, allowingthe vertebral spacer to be attached to adjacent vertebrae. Moreover, itis contemplated that the bone engaging surfaces may be configured,without limitation, to be tapered, concave or convex in order toapproximate the disc space. More specifically, upper and lower boneengaging surfaces may define an angle therebetween for enhancinglordosis of the spine.

[0090] Preferably, implants according to the present invention may havelengths varying from 20 mm to 26 mm. Further, implants may have reducedsize insertion configurations with widths varying preferably between 16mm and 20 mm. Although these dimensions may be used, larger or smallerdimensions may be used without deviating from the scope of theinvention.

[0091] While the invention has been illustrated and described in detailin the drawings and foregoing description, the same is to be consideredas illustrative and not restrictive in character, it being understoodthat only the preferred embodiment has been shown and described and thatall changes and modifications the come within the spirit of theinvention are desired to be protected.

What is claimed is:
 1. A vertebral spacer, comprising: a distal endportion; a proximal end portion positioned opposite said distal endportion; a pair of flexible lateral arms extending between said distalend portion and said proximal end portion; wherein said pair of flexiblelateral arms each have a pair of opposite vertebral bearing surfacesadapted to engage opposing vertebrae; and wherein said pair of flexiblelateral arms are adapted to laterally self-expand from a laterallycontracted position to a laterally expanded position between thevertebrae.
 2. The vertebral spacer of claim 1, wherein said pair offlexible lateral arms each define openings for increasing flexibility ofsaid pair of flexible lateral arms.
 3. The vertebral spacer of claim 2,wherein: said pair of flexible lateral arms, said proximal end portionand said distal end portion define a central cavity adapted to receivebone growth material; and said openings defined in said pair of flexiblelateral arms are adapted permit communication into said central cavity.4. The vertebral spacer of claim 1, wherein said proximal end portiondefines at least one insertion tool opening adapted to receive aninsertion tool.
 5. The vertebral spacer of claim 1, wherein at leastsaid pair of flexible lateral arms are made from a shape memorymaterial.
 6. The vertebral spacer of claim 5, wherein: said pair offlexible lateral arms each define openings for increasing flexibility ofsaid pair of flexible lateral arms; said pair of flexible lateral arms,said proximal end portion and said distal end portion define a centralcavity adapted to receive bone growth material; said openings defined insaid pair of flexible lateral arms are adapted permit communication intosaid central cavity; and said proximal end portion defines a threadedinsertion tool opening adapted to receive an insertion tool.
 7. A spacerfor spacing opposing vertebral bodies, comprising: a spacer body havinga pair of opposite vertebral bearing surfaces constructed and arrangedto engage the opposing vertebral bodies; wherein said spacer bodyencloses a central opening constructed and arranged to hold bone growthmaterial; wherein said spacer body has a height defined by said pair ofopposite vertebral bearing surfaces; and wherein said spacer body isformed from a shape memory material to self-expand said spacer bodylaterally between the vertebral bodies while said height of said spacerbody is unchanged.
 8. The spacer of claim 7, wherein said spacer bodyincludes a pair of lateral members constructed and arrange to laterallyexpand said spacer body.
 9. The spacer of claim 8, wherein said pair oflateral members define openings to allow communication of the bonegrowth material into said central opening.
 10. The spacer of claim 7,wherein said spacer body defines openings constructed and arranged toincrease flexibility of said body portion.
 11. The spacer of claim 7,wherein said spacer body defines an insertion tool opening constructedand arranged to receive an insertion tool.
 12. The spacer of claim 7,wherein said shape memory material includes nitinol.
 13. The spacer ofclaim 7, wherein: said spacer body includes a distal end portion and aproximal end portion; and said spacer body further includes a pair offlexible lateral arms connected to and extending between said distal endportion and said proximal end portion.
 14. A spacer body, comprising: apair of flexible lateral side walls having opposite ends, said pair offlexible lateral side walls being connected at said opposite ends toform a spacer, said spacer having a reduced size configuration with amaximum height and a first maximum width and an expanded sizeconfiguration having said maximum height and a second maximum width,wherein said second width is greater than said first width; and whereinsaid spacer is movable between said reduced size configuration and saidexpanded size configuration by movement of said flexible lateral sidewalls.
 15. The spacer body of claim 14, wherein said flexible lateralside walls are biased to urge said spacer to said expandedconfiguration.
 16. The spacer body of claim 14, wherein said flexiblelateral side walls each defines openings to increase flexibility of saidflexible lateral side walls.
 17. The spacer body of claim 16, whereinsaid flexible lateral side walls define a central cavity to contain bonegrowth material.
 18. The spacer body of claim 14, wherein said spacer ismade from a memory shape material.
 19. The spacer body of claim 14,wherein said opposite ends include a distal end and a proximal end. 20.The spacer body of claim 19, wherein said distal end defines aninsertion tool opening.